Because those spaces are just as accessible from other instances that may not use Lemmy. They’re not on “Lemmy”, they’re on the underlying protocol, i.e. ActivityPub, which is the major part of the fediverse.
It’d be like if you had an Outlook email and instead of referring to it as your email, you refer to it as your Outlook, even though other email implementations can just as easily talk to you. Outlook is just an email implementation, it’s not what email is. That’s the protocol.
Because those spaces are just as accessible from other instances that may not use Lemmy. They’re not on “Lemmy”, they’re on the underlying protocol, i.e. ActivityPub, which is the major part of the fediverse.
It’d be like if you had an Outlook email and instead of referring to it as your email, you refer to it as your Outlook, even though other email implementations can just as easily talk to you. Outlook is just an email implementation, it’s not what email is. That’s the protocol.